1. Technical Field
The present invention relates to a security system utilizing a network built up by using a power line.
2. Background Arts
Over the recent years, every type of device (e.g., an information device, a home electrical appliance, etc.) has been downsized. For example, as for the information devices, there is the spread of down sized versions of a desktop personal computer, a printer, a scanner, which have hitherto been used by installing these devices in fixed positions. Therefore, a convenient environment appears, wherein all types of information devices can be readily carried everywhere without being limited to the notebook type personal computer.
On the other hand, the downsized device is easy to carry and therefore has a great possibility of being stolen, and has a problem in terms of the security in its hands. A security solution as a countermeasure for the downsized device has hitherto been a method for safeguarding by locking the device by use of a security tool such as a chain lock. For others, the information device such as the personal computer takes a method of ensuring the security by use of, e.g., a smart card.
There arise, however, the following problems when adopting the methods described above. Specifically, the device is locked by employing the chain lock, the chain lock might be broken, and there is a case in which the device is easy to be carried out and might be abused intactly. Further, a drawback to ensuring the security by employing the smart card is time-consuming to the user. Namely, in the case of taking the countermeasure for the security using the smart card, the user needs operations of carrying the smart card, inserting the smart card into the device when used and obtaining authentication for using the device by inputting a password.
Moreover, as to the security system, there is a system (Patent document 1) in which a radio signal is transmitted from a broadcasting station in order to prevent, e.g., theft of a car. An assumption in this type of system, however, is a large-scale system based on a wireless base station etc., and hence a tremendous cost is required for building up and preparing an infrastructure including installation of the base station. This type of system is not suited to the system for controlling the downsized devices.
For others, technologies disclosed in Patent document 2 and Patent document 3 are given as technologies related to the present invention.
[Patent document 1]
Japanese Patent Application Publication No.2002-331913
[Patent document 2]
Japanese Patent Application Publication No.3-154436
[Patent document 3]
Japanese Patent Application Publication No.2002-245235